1. Field of the Invention
The present invention relates to a semiconductor device, a method of fabricating the same, a circuit board, and an electronic device.
2. Description of Related Art
Bare-chip mounting is ideal for the miniaturization of a semiconductor device, however, since quality assurance and handling are difficult, the semiconductor device has been processed into a package form. In recent years, a Ball Grid Array (BGA) package has been developed to meet the requirements of high pin counts. The BGA package comprises bumps arranged in an area-array configuration on a substrate as external terminals for surface mounting.
One of the BGA packages is a Tape Ball Grid Array (T-BGA) package in which a tape carrier used in a Tape Automated Bonding (TAB) technology is applied as a base. With this T-BGA package, a semiconductor device which is fine-pitched and realizes high pin counts can be provided by making use of the characteristics of the tape carrier.
However, since this tape carrier lacks rigidity and tends to become warped, it is necessary to apply a support plate (stiffener). The same applies to other flexible substrates than the tape carrier. A stiffener is applied using an adhesive conventionally, giving rise to the problem of complicated application steps.
The present invention solves the aforementioned problem and has an object of providing a semiconductor device produced by simplified steps and a method of fabricating the same, and also providing a circuit board and electronic devices.
(1) A semiconductor device according to the present invention comprises a flexible substrate on which an interconnecting pattern is formed, and a semiconductor chip and a support material that are formed on the flexible substrate using an adhesive; wherein the adhesive is applied at least to a first region of the flexible substrate on which the semiconductor chip is provided, and a second region of the flexible substrate on which the support material is provided.
According to the present invention, the semiconductor chip and the support member are both bonded to the flexible substrate via the adhesive. Accordingly, the adhesive on the flexible substrate bonds both the semiconductor chip and the support member, thereby eliminating the need for providing an adhesive for bonding the support member in addition to an adhesive for bonding the semiconductor substrate.
Therefore, a step of bonding the support member can be omitted.
The support member is for holding the rigidity of the flexible substrate and also contributes to reinforcement of the package. As the support member, for example, rigid materials such as metal plates or materials having high heat resistance are frequently used.
(2) In this semiconductor device, conductive particles may be dispersed in the adhesive, the conductive particles being used to electrically connect electrodes of the semiconductor chip to the interconnecting pattern.
(3) In this semiconductor device, a protective layer may be provided on the interconnecting pattern except areas of connection between the electrodes of the semiconductor chip and the interconnecting pattern.
In this structure, the protective layer protects the interconnecting pattern.
(4) In this semiconductor device, the support member may comprise at least one insulating layer.
This makes it possible to prevent electric conduction between the support member and the interconnecting pattern.
(5) In this semiconductor device, the support member may cover the semiconductor chip.
(6) In this semiconductor device, the support member may be formed of a material with high thermal conductivity.
This support member can also function as a heat-spreader.
(7) In this semiconductor device, the second region may surround the first region.
(8) In this semiconductor device, the support member may hold the flatness of the flexible substrate.
(9) In this semiconductor device, the support member may be thicker than the semiconductor chip.
Because the height of the support member from the flexible substrate is higher than that of the semiconductor chip, the support member can be applied to the flexible substrate without being hindered by the semiconductor device even if a flat tool is used.
(10) In this semiconductor device, a plurality of external electrodes which are electrically connected to the interconnecting pattern may be provided on the surface of the flexible substrate opposite to the surface on which the adhesive is provided.
Since the part of the flexible substrate in which the external electrodes are formed is reinforced by the support member, the coplanarity of the external electrodes can be secured.
(11) In this semiconductor device, the support member may surround the semiconductor chip.
(12) A circuit board according to the present invention is equipped with the above-described semiconductor device.
(13) An electronic device of the present invention comprises the above-described circuit board.
(14) A method of fabricating a semiconductor device according to the present invention comprises the steps of: providing an adhesive on a flexible substrate having an interconnecting pattern; bonding electrodes formed in a semiconductor chip to the interconnecting pattern in a first region of the flexible substrate by the adhesive; and bonding a second region of the flexible substrate that is other than the first region to a support member by the adhesive.
According to the invention, the support member can be applied by making use of the adhesive used for bonding the semiconductor chip to the flexible substrate. Specifically, the support member can be bonded to the flexible substrate only by arranging the adhesive spreading outside the semiconductor chip, whereby the operation of applying an adhesive can be omitted. The support member can be bonded with ease in this manner.
The support member is for securing the flatness of the flexible substrate and also contributes to reinforcement of the package. As the support member, for instance, rigid materials such as metal plates are used in many cases.
(15) In the method of fabricating a semiconductor device, the semiconductor chip may be laid on the adhesive, and pressure may be applied to between the semiconductor chip and the flexible substrate to bond the semiconductor chip.
(16) In the method of fabricating a semiconductor device, conductive particles may be dispersed in the adhesive, and the conductive particles may electrically connect electrodes of the semiconductor chip to the interconnecting pattern by the pressure applied to the adhesive.
(17) In the method of fabricating a semiconductor device, the support member may be laid on the adhesive, and pressure may be applied to between the support member and the flexible substrate to bond the support member.
(18) In the method of fabricating a semiconductor device, the step of applying pressure to between the support member and the flexible substrate may be carried out after the step of applying pressure to between the semiconductor chip and the flexible substrate.
Since the semiconductor chip is applied to the flexible substrate by the face-down bonding, the electrodes can be bonded to the interconnecting pattern before the adhesive deteriorates, and hence better electric connection between them can be assured.
(19) In the method of fabricating a semiconductor device, the support member may surround the semiconductor chip.
(20) In the method of fabricating a semiconductor device, the step of applying pressure to between the support member and the flexible substrate and the step of applying pressure to between the semiconductor chip and the flexible substrate may be carried out at the same time.
In this method, the electric connection of the semiconductor chip and the bonding of the support member can be made simultaneously.
(21) In the method of fabricating a semiconductor device, the adhesive may be formed of a thermosetting material, and the method may further comprise a step of heating the adhesive after the semiconductor chip and the support member are applied to the flexible substrate via the adhesive.
In the case where the adhesive is formed of a thermosetting material, both of the semiconductor chip and the support member can be fixed to the flexible substrate simultaneously by heating them after the both are applied.